T1 independent, T2* corrected MRI with accurate spectral modeling for quantification of fat: validation in a fat-water-SPIO phantom.

PURPOSE: To validate a T(1)-independent, T(2)*-corrected fat quantification technique that uses accurate spectral modeling of fat using a homogeneous fat-water-SPIO phantom over physiologically expected ranges of fat percentage and T(2)* decay in the presence of iron overload.
MATERIALS AND METHODS: A homogeneous gel phantom consisting of vials with known fat-fractions and iron concentrations is described. Fat-fraction imaging was performed using a multiecho chemical shift-based fat-water separation method (IDEAL), and various reconstructions were performed to determine the impact of T(2)* correction and accurate spectral modeling. Conventional two-point Dixon (in-phase/out-of-phase) imaging and MR spectroscopy were performed for comparison with known fat-fractions.
RESULTS: The best agreement with known fat-fractions over the full range of iron concentrations was found when T(2)* correction and accurate spectral modeling were used. Conventional two-point Dixon imaging grossly underestimated fat-fraction for all T(2)* values, but particularly at higher iron concentrations.
CONCLUSION: This work demonstrates the necessity of T(2)* correction and accurate spectral modeling of fat to accurately quantify fat using MRI.